Risk Factors for Anal Continence Impairment Following a Second Delivery after a First Traumatic Delivery: A Prospective Cohort Study

Postpartum anal incontinence is common. After a first delivery (D1) with perineal trauma, follow-up is advised to reduce the risk of anal incontinence. Endoanal sonography (EAS) may be considered to evaluate the sphincter and in case of sphincter lesions to discuss cesarean section for the second delivery (D2). Our objective was to study the risk factors for anal continence impairment following D2. Women with a history of traumatic D1 were followed before and 6 months after D2. Continence was measured using the Vaizey score. An increase ≥2 points after D2 defined a significant deterioration. A total of 312 women were followed and 67 (21%) had worse anal continence after D2. The main risk factors for this deterioration were the presence of urinary incontinence and the combined use of instruments and episiotomy during D2 (OR 5.12, 95% CI 1.22–21.5). After D1, 192 women (61.5%) had a sphincter rupture revealed by EAS, whereas it was diagnosed clinically in only 48 (15.7%). However, neither clinically undiagnosed ruptures nor severe ruptures were associated with an increased risk of continence deterioration after D2, and cesarean section did not protect against it. One woman out of five in this population had anal continence impairment after D2. The main risk factor was instrumental delivery. Caesarean section was not protective. Although EAS enabled the diagnosis of clinically-missed sphincter ruptures, these were not associated with continence impairment. Anal incontinence should be systematically screened in patients presenting urinary incontinence after D2 as they are frequently associated.


Introduction
Anal incontinence (AI) is a taboo condition and a frequent cause of handicap, present in up to 20% of the population [1,2]. Its detection requires a dedicated investigation and can be difficult [3]. Continence is a complex mechanism involving the anal sphincter, rectal compliance, anorectal angulation, pudendal nerve innervation and the nature of the stools. Incontinence occurs when one or more of these mechanisms is altered beyond compensation [4]. Aging leads to a decrease in muscle and perineal trophicity and is one of the main risk factors for AI [5]. Various events in perineal life will accelerate this aging. Childbirth is one of these disruptors of pelvic integrity. The damage it causes to the perineum (mostly anal sphincter injury and pudendal nerve stretching) is frequent, affecting Our work is an ancillary study of the prospective, randomized, multicenter "Prevention of Anal Incontinence by Caesarean Section" (EPIC) study, which compared the benefit of prophylactic caesarean section (CS) to vaginal delivery (VD) at D2 in women with a history of a traumatic D1 with sphincter rupture confirmed by EAS [8]. Women were recruited in six maternity units in the Paris area between April 2008 and December 2014. They were included by their gynecologist during the 3rd trimester of their 2nd pregnancy if they met the inclusion criteria, which were as follows: a single history of traumatic vaginal delivery (VD), defined as forceps extraction or with grade III perineal tear (reaching the sphincters), age above 18 years old, informed written consent and no AI at inclusion, based on a YES/NO answer to the question asked by the gynecologist. They were excluded if they had a history of grade IV perineum tear (which corresponds to the most severe grade of OASI with sphincter and anal mucosa damage) and if a CS was indicated for their future delivery for a non-proctological reason. After inclusion, systematic prospective follow-up was carried out, with a proctological examination during the 3rd trimester of their 2nd pregnancy (referred to as before D2 visit) and then 6 months after the second delivery (referred to as after D2 visit). This visit included questionnaires measuring the Vaizey score for anal continence and the measure of urinary handicap score (MHU) for urinary continence, as well as an EAS.
In the EPIC study, women with EAS sphincter rupture were randomized to perform D2 by VD or CS. Some women included in EPIC were not randomized, either because EAS did not reveal a sphincter rupture or because they refused randomization. The mode of delivery was then discussed between the obstetrician and the patient. In this study, we included all women who were explored by EAS before D2 and for whom a Vaizey score was calculated before and after D2, regardless of their randomization status.

Objective and Thresholds
The analysis of anal continence was based on the Vaizey score [22] (Appendix A). Data differs in the literature to assess which Vaizey value significantly defines incontinence [23]. In the EPIC study, based on this literature and on expert opinion, a score ≥5 defined AI [8,24]. Our population being inhomogeneous regarding continence before D2, we selected as the primary endpoint worsening of the Vaizey score after D2, defined as an increase ≥2 points in the score between the two proctological examinations. Comparable definitions were used in previous proctologic studies [25].
Because transient AI (lasting less than 2 months) is common in the immediate postpartum period [26,27], the assessment 6 months after D2 was used to measure persistent continence deterioration.
EAS was performed by a single trained operator, using a rotating rectal probe (7-10 MHz, Brüel and Kjaer). Upper, middle and lower anal canal were studied. A sphincter lesion was identified as a loss of continuity visible by a change in echogenicity within the sphincter ring [28]. Severity was assessed based on the Starck score (Appendix B). A score ≥9 was used to define a severe sphincter rupture [29,30]. The clinical description of perineal lesions was based on the Royal College of Obstetricians and Gynecologists classification, where the anal sphincter is considered impaired in grades III and IV (Appendix C). We defined a "hidden sphincter rupture" as a tear undiagnosed in the delivery room (or underdiagnosed as a grade I or II) but observed by EAS. After D2, ruptures were considered "de novo" if no EAS defect was visible after D1.
The analysis of urinary continence was based on the MHU score (Appendix D) [31], treated as a continuous variable ranging from 0 to 28 points. Macrosomia was defined by birthweight >4 kg [32]. Birthweight was not collected in D2 in the case of CS. Instrumental delivery referred to the use of all types of forceps or vacuum but the type of forceps was not specified. Details of the episiotomy were not collected. We defined "abnormal transit" as the presence of diarrhea, constipation or dyschesia. We asked the patients whether or not they had undergone perineal rehabilitation, but the modalities were not collected (number of sessions or technique used).

Statistical Analysis
Categorical variables were described as numbers and percentages and quantitative variables were described as median and interquartile ranges. We compared median Vaizey scores at the two visits with Wilcoxon paired tests. To assess the association between the primary outcome and the characteristics of the women, univariate logistic regressions were performed to determine unadjusted odds ratios (OR) and their 95% confidence intervals. Variables with a univariate p value < 0.20 were tested in multivariate models. Variable selection for the final multivariate model was performed using top-down selection with the Akaike information criterion. The linearity assumption was tested graphically and with the Wald test for the MHU score. An analysis on the subgroup of women giving birth by VD at D2 was conducted using the same methodology, to study the impact of a second vaginal delivery and its characteristics. p values < 0.05 were considered significant. The tests were two-sided. All analyses were performed using R software (v.3.4).

Participants
A total of 549 parturients were included in the EPIC study, of which 312 had a Vaizey score completed before and after D2 and were included in our ancillary work ( Figure 1). Characteristics of the population are described in Table 1

Participants
A total of 549 parturients were included in the EPIC study, of which 312 had a Vaizey score completed before and after D2 and were included in our ancillary work ( Figure 1). Characteristics of the population are described in Table 1.
In multivariate analysis, delivering by CS did not impact significantly the risk of worsening continence after D2 compared to VD (Table 5). Women who were already incontinent before D2 were less likely to deteriorate in their Vaizey score after D2 (OR 0.27-95% CI 0.08-0.86). Increase in MHU score after D2 was linearly associated with a risk of continence deterioration (OR increased by 1.24 per MHU point-95% CI 1.08-1.42).

Among the 193 Patients That Delivered Vaginally at D2
In this subgroup, in univariate analysis, macrosomia, the absence of perineal rehabilitation after D1 or D2 and the presence of an endosonographic or clinical sphincter rupture were not associated with an increased Vaizey score after D2 (Table 6). Instrumental delivery, with or without episiotomy, increased the risk of worsening anal continence after D2. We did not find a significant association with episiotomy itself.
In multivariate analysis (Table 7), instrumental delivery or episiotomy were associated with a deterioration of anal continence only when performed together (OR 4.18-95% CI 1.05-16.59). Increase in MHU score after D2 was linearly associated with a risk of AI (OR1.25 per MHU point-95% CI 1.11-1.43).

Sphincter Tears before D2
192 (61.5%) women had an EAS sphincter rupture before D2, whereas only 48 (15.7%) had a grade III OASI clinically recognized by the obstetrician in the delivery room during D1. These hidden ruptures were not accompanied by an increased risk of continence impairment after D2 ( Table 2). The description of sphincter ruptures is provided Appendix E.

Sphincter Tears after D2
A total of 143 (71.9%) women had sphincter ruptures revealed by the EAS performed after D2 (out of 199 who underwent EAS). Only six had "de novo" sphincter ruptures. These were women who had delivered vaginally, including one with episiotomy. The subgroup was too small to evidence a significant association between these ruptures and continence impairment in univariate analysis.

Main Results
To our knowledge, this study is the largest prospective cohort describing risk factors for continence impairment after a second delivery in at-risk parturients. The main risk factor was instrumental extraction coupled with an episiotomy during a second vaginal delivery. These results are consistent with the literature and the absence of an increased risk related to episiotomy when analyzed independently is reassuring regarding the controversial impact of this procedure [7,24].
The risk factors of postpartum AI are still debated. Forceps delivery and perineal tears are frequently associated with AI [7,11,13,33]. But the association is less clear for episiotomy, multiparity [7,11], macrosomia and nulliparity [13]. In our work, none of these factors were associated with an increased risk of continence impairment after D2, possibly because we studied at D2 the impact of some events occurring at D1 and because we relied on a large and prospective cohort, unlike previous studies.
We found a strong association between the presence of urinary incontinence after D2 and the presence of AI. Patients and their physicians are often aware of the risk of urinary incontinence after delivery, while the diagnosis of AI is more challenging. The diagnosis of urinary incontinence could initiate dialogue between the obstetrician and the proctologist.
At inclusion, several women denied having AI during non-specific questioning, while a more focalized interview during the proctological consultation enabled a proper continence evaluation.
Surprisingly, the presence of AI before D2 was associated with a decreased risk of continence impairment after D2. We assume that some women had signs of AI related to the pregnancy itself, due to transit and pelvic static disorders, which improved after the delivery.
CS was not associated with a decreased risk of continence impairment after D2. This is consistent with the EPIC study [8] and recent literature [34,35].

The Place of EAS
Women with traumatic deliveries are routinely offered EAS examination in order to detect a clinically undiagnosed sphincter defect. We indeed observed that among half of the patients, an anal sphincter rupture had been missed clinically but was evidenced by EAS, which is consistent with the literature [6,9].
The EPIC study demonstrated however, that it was not beneficial to perform prophylactic cesarean section to these patients to prevent the occurrence of AI after D2 [8]. Our study goes further, showing that neither the presence of these hidden sphincter ruptures diagnosed before a second delivery, nor even the most severe sphincter tears, were associated with a significant risk of continence impairment after D2. We therefore have no argument for advocating the use of EAS after a first traumatic delivery. However, in our practice, performing an EAS, as frequently requested by maternities, allows these women at-risk to have access to a proctologist, who can inform them about long-term risk factors for AI and avoidable cofactors.
These results can be challenged by the relative scarcity of severe sphincter tears in our study, mostly because of the low percentage of internal sphincter injuries, which strongly impacts Starck's score [29,30]. In Sultan's cohort [9], 16% of women had an internal sphincter defect versus only 5.8% in our study. These results may be explained by the exclusion of patients with grade IV perineal tears or already reporting AI to their gynecologist after D1. There is therefore still room to debate the benefits of EAS among these patients.

Strengths and Limitations
We collected data in medical centers representative of the population pools of our region and we relied on validated clinical criteria (Vaizey score, MHU score) and paraclinical criteria (Starck's score [29,30]). EAS were performed by a single expert operator, which limited ranking bias by preventing inter-operator variability. Moreover, the inter-operator concordance of this practitioner had already been validated in a previous work [7].
There is no consensus on thresholds defining AI in literature. We chose to define a continence impairment as an increase in two points of the Vaizey score after D2. This is a sensitive threshold for continence deterioration but not a very specific one.
Anal incontinence tends to decrease in the weeks following delivery and to reappear after menopause. One of the limitations of this work is the lack of follow-up beyond one year after D2.
Although the follow-up was prospective, we conducted this work after the legal closing date of the original study, which prevented us from completing the missing data. Therefore, 122/434 (28%) of women who underwent EAS before D2 were not analyzed. However, we did not evidence any difference between the baseline characteristics of our population and this unanalyzed population (Appendix F).

What Can Be Offered to a Woman at Risk of Continence Impairment after D2
Potential perineal damage risk can be reduced by measures such as regulating transit, treating dyschesia (source of pudendal stretch or prolapse) and avoiding additional sphincter trauma as much as possible. It is thus advisable to refer women at risk or presenting postpartum AI to proctologists for multi-disciplinary management.
Although the main risk factor for continence impairment is forceps delivery with episiotomy, these obstetrical interventions are sometimes necessary and cannot be completely avoided.
In case of proven AI and after managing possible cofactors, pelvic rehabilitation with biofeedback or neuromodulation of the sacral roots may be beneficial [36][37][38].

Conclusions
After a first traumatic delivery, instrumental delivery with episiotomy is the main risk factor for anal continence impairment during a second delivery. Women who present symptoms of urinary incontinence after their second delivery also are at greater risk of developing symptoms of anal incontinence. Referral to a proctologist will improve the detection and management of this incontinence. Caesarian section does not prevent it. In a woman wishing to start a second pregnancy after a first traumatic delivery, the presence of a sphincter lesion on endoanal ultrasound will not change the course of treatment.

Institutional Review Board Statement:
This study is an ancillary study of the randomized EPIC study (Abramowitz et